dart2js cps: Support sync* and yield.

pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart

Index: pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
diff --git a/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart b/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
index c4b993b008ecddc38eafb113b9fffec324d8f58c..8adf3a9171e3a46432e915c49a531b6d1b8fd60c 100644
--- a/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
+++ b/pkg/compiler/lib/src/tree_ir/tree_ir_builder.dart
@@ -436,6 +436,19 @@ class Builder implements cps_ir.Visitor/*<NodeCallback|Node>*/ {
     return makeCallExpression(node, value);
   }
 
+  @override
+  NodeCallback visitYield(cps_ir.Yield node) {
+    return (Statement next) {
+      return new Yield(getVariableUse(node.input), node.hasStar, next);
+    };
+  }
+
+  @override
+  NodeCallback visitAwait(cps_ir.Await node) {
+    Expression value = new Await(getVariableUse(node.input));
+    return makeCallExpression(node, value);
+  }
+
 
   /************************** TAIL EXPRESSIONS  **************************/
   //
@@ -670,12 +683,6 @@ class Builder implements cps_ir.Visitor/*<NodeCallback|Node>*/ {
   }
 
   @override
-  NodeCallback visitAwait(cps_ir.Await node) {
-    Expression value = new Await(getVariableUse(node.input));
-    return makeCallExpression(node, value);
-  }
-
-  @override
   Expression visitRefinement(cps_ir.Refinement node) {
     throw 'Unexpected Refinement node in tree builder';
   }